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Synopsis of animal classification,

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GAYLORD

Cornell University

The original of this book is in
the Cornell University Library.

There are no known copyright restrictions in
the United States on the use of the text.

http://www.archive.org/details/cu31924002815334

A SYNOPSIS

OF

ANIMAL CLASSIFICATION

BY

HARRIS HAWTHORNE WILDER, Px.D.

Professor of Zodlogy in Smith College

4
4

NEW YORK

HENRY HOLT AND COMPANY
1902

CH.
£82 2

VSG
@ 17 £9

Copyright, 1902,
BY
HENRY HOLT & CO,

ROBERT DRUMMOND, PRINTER, NEW YORK

PREFACE.

THERE is, perhaps, nothing about the science ot Zodlogy which
is so much a matter of individual opinion as the method of classifica-
tion of the various animal forms; and this is so in the nature of
things, since a classification is at best but an artificial arrangement for
convenience, and only in an incomplete and wholly inadequate way
represents the actual relationships. These difficulties have led many
teachers to practically disregard classification altogether ; but what is
thus gained in scientific accuracy is lost in clearness of arrangement,
and the whole study is apt to seem vague and uncertain. It is to pre-
vent this feeling of vagueness, and to furnish a foundation by means
of which the facts ascertained by the student may be arranged in
logical sequence, that I have attempted this outline, and in this
attempt I have sought to present a classification which is modern and
rests upon a morphological basis, but is, at the same time, one that is
dependent upon obvious points of structure, and is thus not too tech-
nical for the use of beginning students.

In the artificial key at the end there is no attempt at morphological
grouping, and the characters emphasized are, as far as possible, the
most obvious ones. Its main value is that of an index by means of
which a student who investigates an animal for the first time may
guide himself to the proper part of the synopsis without being under
the necessity of applying to the instructor.

Dryaps’ GREEN,
NoRTHAMPTON, MAss.,
September, 1902.
iii

A SYNOPSIS OF ANIMAL CLASSIFICATION.

I. MAIN SUBDIVISIONS OF ANIMALS.

All known animals, both recent and fossil, may be conveniently
grouped in the following eight subdivisions, or Types:

Type I.
Type II.

Type III.

Type IV.

Type V.

Type VI.
Type VII.

Type VIII.

PROTOZOA..........

Ameeba, Infusoria, monads, etc.

C@LENTERATA ....Hydroid polyps, jelly-fish, corals,

VERMES...........-

MOLLUSCA..........

ARTICULATA.......

sponges, etc.

Unsegmented worms, both free
and parasitic; rotifers, brachio-
pods, etc.

Bivalves, like clams and oysters ;
snails and slugs; cuttlefish, squid,
etc.

Segmented worms like earth-
worms and leeches; crustaceans,
insects, spiders, mites, etc.

ECHINODERMATA ..Star-fish, sea-urchins, etc.

PREVERTEBRATA..Balanoglossus, tunicates, Amphi-

oxus.

VERTEBRATA .....- Fishes, amphibians, reptiles, birds,

and mammals.

The idea of thus arranging animals in Types or fixed groups de-
veloped mainly under the influence of Linnzeus, Cuvier, and Agassiz,
who taught that each Type was in itself absolutely distinct from all

2 A SYNOPSIS OF ANIMAL CLASSIFICATION.

others and represented a certain definite plan of structure having no
relation to the rest. Later investigation, however, has altered the
significance of the Types, and what were once considered as distinct
and unrelated animal groups are now seen to be but convenient divi-
sions, based upon the actual structure of living animal forms and of
the few extinct ones the remains of which have come down to us,
and more or less organically connected with one another.

Among the modifications of this arrangement since the time of
Cuvier are (1) the introduction of several new types, and (2) the
grouping of the types thus established into larger groups in an
attempt to express the various interrelations which exist between
them. ‘Thus the Protozoa, which are unicellular, and consequently
without tissues, are contrasted with the Metazoa, which are multi-
cellular, possess tissues and include all other animals.

The Metazoa, again, are divided into those composed of but two
germ-layers and with a single internal cavity, and those composed of
three germ-layers and with one or more cavities (ccelomes) interposed
between the central cavity and the exterior, the two groups thus repre-
senting a single and a double tube respectively. Of these the first in-
cludes the single Type of Ceelenterata (Type II), while the remainder
are taken together to form the contrasting group of Celomata.

These latter Types (III-VIII) are again divided into three subdivi-
sions, probably representing as many main branches or lines of descent :
(1) the Zygoneura, including Vermes, Mollusca, and Articulata
(Types III-V), and characterized by a nervous system of paired
ganglia placed ventrally ; (2) the Ambulacralia, including the single
Type of Echinodermata (Type VI), animals which are bilateral when
young and radiate when adult, and which are furnished by a water-
vascular system terminating externally in a series of ambulacral feet ;
and (3) the Chordata, which include the Prevertebrata and Verte-
brata (Types VII, VIII), and are characterized by the presence of a
dorsal nervous system and a central skeletal axis, the zofochord, about
which in the higher forms an internal skeleton becomes developed.

Certain of the Types include within their limits forms possessing
structural differences of too fundamental a character to allow of their
consideration as a single unified group, and yet conforming too closely
in general plan to allow the formation of new Types. In such cases it

I, MAIN SUBDIVISIONS OF ANIMALS. 3

is well to employ subdivisions, which may be called Sub-Types, and
which will separate a Type into two or three distinct groups. Such
divisions may be conveniently used in the case of the Calenterata, where
the polyps and medusz, the Ctenophores and the sponges all represent
the Ccelenterate plan of structure, yet are radically different from one
another, and in the Ar/culafa, where the Annelids with their jointless
appendages, the parapodia, may be separated from the Arthropods,
which possess jointed limbs, the meropodia.

A summary of the above relations may be expressed by the follow-
ing table, in which are expressed the grouping and subdivision of the
Types:

I. PROTOZOA.

Type I. Protozoa.

II], METAZOA.
A. CHELENTERATA.

Type II. Cca@LenTERATA,
Sub-type I. Cnidaria,
Sub-type II. Ctenophora.
‘Sub-type III, Porifera,*

B. CELOMATA.

1) Zygoneura.
Type III, Vermes.
Type IV. Mo .tusca.
Type V. ARTICULATA,
Sub-type I. Annelida.
Sub-type II, Arthropoda,
2) Ambulacralia.
Type VI. EcHINODERMATA.
3) Chordata.
Type VII. PREVERTEBRATA.
Type VIII, VERTEBRATA.
* According to the more usual arrangement of the three Sub-Types of the
Ceelenterata the Porifera are placed first on the ground of the semi-independ-
ence of the cells and the consequent resemblance to a colony of Protozoa. In other

respects, however, the Porifera are much modified and in their architecture and
skeletal structure they are more complex than are the two other Sub-Types.

4 A SYNOPSIS OF ANIMAL CLASSIFICATION.

The artificial character of this and all forms of classification is well
seen in the fact that scarcely any two zodlogists will agree exactly on
the arrangement of the groups. Thus, with regard to the above
table, some prefer to raise the three sub-types of Cnidaria, Cteno-
phora, and Porifera to the value of Types and to use the word
“* Celenterata’’ only as an antithesis to that of Calomafa, Others
regard the grouping expressed by the terms Zygoneura, Ambulacralia,
and Chordata as of little value, and would employ the term ‘‘Chordata’’
as the equivalent of Vertebrata (Type VIII), or, again, would reduce
the Types VII and VIII of the above table to the rank of sub-types
under the Type Chordata. A common usage raises the ‘‘ Sub-Type IT.
Arthropoda’’ to the rank of a Type, and unites ‘‘Sub-Type I. Annelida’
to the Vermes (Type III). These differences of individual opinion
rest upon the varied emphasis placed upon certain points of structure,
or, perhaps, upon convenience to the memory and for purposes of in-
struction, and serve but to emphasize the facts that the animal forms
available for study are but detached fragments of a once continuous
history, and that the position of these fragments is in many cases
a doubtful one. ,

Il. THE TYPES IN DETAIL WITH THEIR SUBORDINATE
GROUPS.

TYPE I. PROTOZOA.

Unicellular organisms, single or colonial. Reproduction by fis-
sion or gemmation, also by conjugation, which may simulate sex-dif-
ferentiation. Colonial forms may show a slight degree of polymor-
phism with division of labor, thus serving as transition forms between
Protozoa and Metazoa.

Class I. RHIZOPODA............ No cell-wall; move by pseudo-
podia.

Order 1, PRoTopuasta........Naked, or with shell made of
chitin, sand-grains, etc., and con-
taining a single large opening, out
of which the animal extends its

pseudopodia.
Sub-order 1. Protoplasta
LOD08G sie nace ie eawaa ee With thick, generally rounded
pseudopodia.

x Amaba, Difiugia.
Sub-order 2. Profoplasta

fHOSAss vine oserweg 3 wei sis 8% With fine, thread-like pseudopodia.

x Euglypha,

Order 2. FORAMINIFERA...... Calcareous shell, perforated with

innumerable fine openings; all

marine. x Globigerina, Rotalia,

Order 3. RADIOLARIA........ Silicious shell, generally lace-like ;
marine.

x Thalassicolla, Acanthometra.
5

Order 4. HELI0z0A

Class II. INFUSORIA

Order 1. CILIATA......

Sub-order 1. Holotricha

seo wee

Sub-order 2. Heterotricha...

Sub-order 3. Pertiricha......

Sub-order 4. Hyporricha...

Order 2. SucToRIA

re

Class III, MASTIGOPHORA

Order 1. NUDOFLAGELLATA....
Order 2. CHOANOFLAGELLATA. .

Order 3. CILIOFLAGELLATA....

Order 4. CYSTOFLAGELLATA....

Supplementary Order. VoLvocin.

Many of the lower plants are,

Flagellates, and thus the plants an

A SYNOPSIS OF ANIMAL CLASSIFICATION.

Usually fresh-water forms; mostly
spherical in shape, with silicious
spicules.

x Actinophrys, Clathrulina.

. Cell-wall present, furnished with

cilia or with knobbed tentacles.
Body ciliated ; usually locomotive ;
a few sessile forms.
Cilia uniformly covering the body.
x Paramecium.
Cilia in patches, and often of dif-
ferent lengths. x Stentor.
Cilia in a ring around the mouth.
x Vorticella, Epistylis.

.Cilia only underneath; creeping

forms. x Stylonychia.
Certain areas of body prolonged
into attenuated tentacles tipped
with adhesive knobs. x Acimefa.
Cell-wall present ; move by one or
more flagella; solitary and colo-
nial forms.
Simple monads, solitary or colonial.
x Cercomonas.
Collared monads, often colonial.
x Codosiga.
Mostly marine forms, with siliceous
exoskeleton.
x Ceratium, Peridinium.
Large marine forms, with reticu-
lated endoplasm. x Noctiluca.
‘A: Large, spherical colonies contain-
ing specialized macro- and micro-
zooids for reproduction, May
probably be classed as plants.

at least in certain stages, typical
d animals come in contact at about

Il, TYPES IN DETAIL WITH THEIR SUBORDINATE GROUPS. 7

this place. In many cases it is impossible to tell with certainty whether

the organism in question is a plant or an animal, and the decision rests

upon a common agreement rather than upon any definite structure or
physiological reaction.

Class IV. SPOROZOA............ Parasitic Protozoa with a compli-
cated life-history, one stage of
which is usually a cyst or case con-
taining numerous minute individ-
uals called spores. Recently this
class has acquired a great though
unpleasant notoriety through the
establishment of the fact that sev-
eral of our worst diseases, such as
malarial and yellow fevers, are
caused by members of this group,
one stage of which is passed in
the human blood, while various
species of mosquito serve as the
intermediate host.

x Monocystis (in earthworms),
Hamameba (in blood of verte-
brates and in insects).

TYPE Il. CCELENTERATA.

Animals built on the plan of a Gasfruda, i.e., that of a cup or
vase with double walls, ectoderm and endoderm; with a large cen-
tral cavity, the gastroccele, and with a mouth or protostome. They
are strictly radial in structure and possess a central axis and two
poles, oral and apical. The parts are arranged about the axis in
2°, 45, 6° and their multiples. A fundamental difference in the
three sub-types, although seen in some of them only in the embryo,
is the difference in development and use of the apical pole.

In the sessile Cuzdaria it is used as the point of support, and is
non-sensitive in the free-swimming ones; in the Cvenophora it is di-
rected forward during locomotion and bears the principal sense-
organs; and in the Porzfera it is the point at which the excurrent
orifice, the osculum, is situated.

8 A SYNOPSIS OF ANIMAL CLASSIFICATION.

Sus-type I. CNIDARIA.

Sessile forms known as folyps, and free-swimming ones known
as meduse@, often occurring as various generations of the same species.
Tentacles are almost universally present, and these and other exposed
parts are armed with cnidoblasts, or ‘‘nettle-cells.’’

Class I. HYDROZOA............ Animals based upon the plan of a
simple polyp, the Hypruta.

Order 1. AUTHYDRE.......... Polyps which produce other polyps
without an intervening medusa-
generation.

Sub-order 1. Mydrida....... Simple, fresh-water polyps. In-

dividuals solitary, not forming col-
onies. Reproduce asexually in
summer and sexually at the ap-
proach of winter. x Hydra.
Sub-order 2. Aydrocoralline.Tropical marine forms in poly-
morphic colonies, producing a sort
of coral. x Millipora.
Order 2. Hypro-mMepus#.....Polyps of the hydrula form, and
small medusz with velum; these
forms usually appear as alternate
generations of the same animal.
Sub-order 1. Gymnoblastea-
anthomedus@ ........ .... Sessile colonies of polyps with re-.
productive medusz, free or re-
duced. The polyps are naked, i.e.,
not protected by the perisarc.
The medusz possess ocelli and
genital organs in the manubrium.
x Pennaria (with reduced meduse),
Podocoryne (with free medusa, the
form called Dysmorphosa).
Sub-order 2. Cualyptoblastea-
Leptomedus@ 6... cee vevas Sessile colonies of polyps with re-
productive meduse, free or re-

Il. TYPES IN DETAIL WITH THEIR SUBORDINATE GROUPS. 9

duced. The polyps are protected
by cups formed of the perisarc.
The medusz possess otocysts and
genital organs on the radial canals.

x Campanularia.

Sub-order 3. Zrachymeduse. .Free-swimming medusz with ve-
lum, 4-6 radiating canals and other
characteristics of Hydro-meduse,
but with direct reproduction and
no polyp generation.

x Liriope, Geryonia.

Sub-order 4. Szphonophora. ..Free-swimming colonies of poly-
morphic individuals representing
both types (polyp and medusa) and
characterized by a complex of sev-
eral individuals, known as a Cor-
midium,

x Velella (with free medusz).

Physalia (with reduced medusz,

which remain attached to the
colony).

Class II. SCYPHOZOA........... Animals based upon the plan of a
polyp with invaginated manubrium,
and with mesenteries, the ScypHuULA.

Order 1. ANTHOZOA........... Scyphula polyps which produce
other polyps without medusa gen-
eration; thus corresponding to the
Authydre above. Mostly coral
producers.

Sub-order 1. Hexacoralla....Mesenteries and other parts in 6°,
Some forms (the ‘‘sea-anemones’’
produce no coral; others form at
the base of the polyps a solid mass,
often branched, and showing pits
and radiate partitions to mark the
site of the individual polyps.

x Metridium, Fungia.

10 A SYNOPSIS OF ANIMAL CLASSIFICATION.

Sub-order 2. Octocoraile....Mesenteries and tentacles always
eight; coral consists of a horny
axis about which is built a polypa-
rium containing calcareous spicules
called sklerites,

Renilla, Corallium,

Order 2, ScyPHO-MEDUSEZ...... Large meduse without velum,
which are produced by minute

polyps of the scyphula type. This

order corresponds to that of the

Hydro-medus@ above, although here

the medusa form is by far the most

in evidence. Cyanea, Aurelia,

Supplementary class: PLANULOIDEA. Minute endoparasites, with-
out mouth or intestinal lumen, resembling the Planula larva of Cnidarian
polyps. There are two groups: the Dzcyemzdz, found in the nephridia
of Cephalopods, and the Orthonectide, in Ophiuridea, Turbellaria, and
Nemertea. They have been considered as “ Mesozoa,’”’ intermediate

between Protozoa and Metazoa, but are more probably Cnidaria, reduced
by parasitism.

Sus-tyez II. CTENOPHORA.

Floating pelagic forms, transparent and gelatinous, with eight
rows of swimming-paddles. Structure a modified radiate or doubly
bilateral one. No nettle-cells, but somewhat similar organs, and
adhesive cells.

Class I. TENTACULATA......... With two long prehensile thread-
like tentacles. x Pleurobrachia.
Class II, NUDA................ Tentacles wanting. x Beroé.

Sus-type III. PORIFERA.

The typical members of this group are shaped like polyps with-
out tentacles, but with the lateral walls perforated by numerous
incurrent pores and with a large excurrent orifice, the osculum, at
the top. They possess between ectoderm and endoderm a mass of
cells, the mesenchyme, containing spicules or a network of horn-
threads. The more modified forms often grow into masses, the
individuals of which cannot be definitely distinguished.

I.

Class I. CALCISPONGLE

Order 1. AsconriDA

Order 2. Syconrpa

Order 3. Lruconipa

Class II. SILICISPONGLE........
Order 1. TETRACTINELLIDE...
Order 2. HExAcTINELLIDE

Class III. KERATOSPONGLE

TYPE III.

TYPES IN DETAIL WITH THEIR SUBORDINATE GROUPS.

. Skeleton

II

Skeleton composed of calcareous
spicules, the typical form of which
is a three-pointed star.
Wall of sponge not folded—main
cavity lined with digestive cells.
x Ascetia.
Wall of sponge forming oblong
chambers opening directly into the
main cavity. Digestive cells con-
fined to the chambers.
x Sycandra.
Wall of sponge with a very thick
mesoderm, in which are spherical
chambers lined with digestive en-
dodermal cells. Chambers con-
nected with the exterior and with
the main internal cavity by branch-
ing canals. x Leucandra.
Skeleton composed of silicious
spicules, often in the form of simple
rods, or in some cases showing de-
signs based upon the number 6.
containing four-rayed
spicules.
Skeleton containing six-rayed spic-
ules. x Euplectella, Hyalonema.
Skeleton of chitinous threads form-
ing a network, sometimes rein-
forced by silicious spicules.
x Luspongia,

VERMES.

A large and heterogeneous group of low Invertebrates placed

for convenience under a single Type.

Although many members of

the group are cylindrical and worm-like in shape, there are many

other forms included.

They are all soft-bodied, with a thin ex-
ternal cuticle, and with no internal skeleton.

None are segmented,

12 A SYNOPSIS OF ANIMAL CLASSIFICATION.

although in one group a reduplication of certain parts resembles a
definite segmentation. The nervous system consists of a central
ganglion at the anterior end, from which extend longitudinal cords
which in the case of the more attenuated forms may become a com-
plicated system with transverse commissures. Many are sessile or
possess organs for temporary attachment; in the locomotive forms
motion is effected by contractions of a subcutaneous muscular layer,
or in a few primitive and minute forms, by a band of cilia, the
trochus. A large number of Vermes are parasitic.

Class I. PLATYHELMINTHES.....Vermes flattened dorso-ventrally,
and with the body-cavity entirely
filled with a tissue known as Paren-
chyma, necessitating in the larger
forms a dendritic branching of
alimentary and other systems.
Intestine incomplete (i.e., without
anal orifice). Hermaphroditic.

Sub-class I. TURBELLARIA........ Free-swimming Platyhelminthes,
of oval shape; body very contractile
and covered with cilia,

Order 1. RuaBDOCELA........ Intestine a straight, unbranched
tube. x Mesostomum,
Order 2. TRICLADA........... Intestine dendritic, with three main
trunks—one anterior and two pos-
terior. x Planaria.
Order 3. PotyctaDa.........- Intestine like foregoing, but with

more than two posterior branches.
x Planocera.
Sub-class II. TREMATODES....... Parasitic Platyhelminthes. Boyd
not ciliated in the adult, but gen-
erally furnished with sucking-discs.

Intestine much as in Triclada.
Order 1. MonoGEnga......... Ecto-parasites upon gills, integur
ment, bladder, etc., of aquatic ver-
tebrates. Sucking-discs, three o-

more. Development direct.

x Polystomum.

I, TYPES IN DETAIL WITH THEIR SUBORDINATE GROUPS. 13

Order 2. DIGENEA............ Ento-parasites with never more
than two sucking-discs, Develop-
ment by heterogony, through forms
known as sporocyst, redia, cercarta,
etc., which inhabit several hosts,
the first being a pond-snail or some
allied form.

x Fasciola (Distomum).
Sub-class III. CEsTopEs......... Ento-parasitic | Platyhelminthes
without intestine. Adult form
generally composed of links (pro-
glottids). Larval form (cysticercus)
provided with sucking-discs, and
often hooks. In the typical forms
the cysticercus encysts itself in the
muscles or internal organs of its
first host, and develops into the
link-form only when swallowed
by some special animal, which
thus serves as its second host.
x Tenia.

Supplementary group: NEMERTEA or NEMERTINI. A group of free-
living worms, mostly marine, with a few representatives in fresh water
and in damp earth. Their position in the system is uncertain, but they
seem in most characteristics to be allied to the PLATYHELMINTHES,
Like them they are dorso-ventrally flattened, and possess lateral excre-
tory canals and diverticula to the intestine; their nervous system is also
similar. They differ, however, in the possession of a body cavity, a set
of blood-vessels, and a complete alimentary canal with anus. At their
anterier end they possess a long retractile proboscis. The more typical
marine forms have a minute ciliated larva called a fzlzdzum. Some are
small, a few marine forms attain a great length (30-40 feet), They are
divided into three orders, as follows :

Order 1, HOPLONEMERTINI...... Proboscis armed with bristles.
x Tetrastemma.
Order 2, SCHIZONEMERTINI..... Proboscis unarmed, head nearly
divided by deep, longitudinal fis-
sures. x Cerebratulus.
Order 3. PALHONEMERTINI..... Proboscis unarmed. Head nearly
entire. x Cephalothrix.

Class II. NEMATHELMINTHES. ..Cylindrical worm-shaped Vermes,
possessing a body cavity. Intes-

14

Sub-class I. NEMATODES

A SYNOPSIS OF ANIMAL CLASSIFICATION.

tine, when present, usually com-

plete.
Long, cylindrical unsegmented
worms. Body not contractile but

very pliable. Two lateral excre-
tory canals. Intestinal canal long
and straight, with mouth and anus
generally present. Sexes usually
separate. Free-swimming and
parasitic forms.

x Ascaris, Trichina.

Supplementary form. Sagztfa, a small marine worm with caudal and

lateral fins, and a paired group of bristles which serve as jaws.
assigned to a separate order—Chetognatha.

Sub-class II. ACANTHOCEPHALI....

Class III. TROCHELMINTHES.....

Sub-class I. ROTIFERA...........

Order 1. CEPHALOTRICHA

Is
(Cf. p. 21.]

A single family of worms, externally
similar to last, but with an ante-
rior extensile proboscis beset with
hooks, and no intestinal canal.
Larval stage in crustaceans and in-
sects; adult in intestine of verte-
brates. x Lichinorhynchus.
Vermes of various shape, never
worm-like, and usually minute.
The locomotive species possess a
ciliated band or ¢rochus, which, in
the sessile forms, is represented
by ciliated tentacles.
Minute locomotive Trochel-
minthes, with ciliated areas and
generally a few posterior segments.
True rofz-fers (i.e., wheel-bearers),
with cilia at the anterior end,
usually covering two protrusible
organs resembling wheels.

x Brachionus, Rotifer.

I. TYPES IN DETAIL WITH

Order 2. GASTROTRICHA

ee eee ee

Sub-class II. BRY0ZO0A (POLYZOA) .

Order 1. PHORONIDEA

Order 2. Enpoprocta

Order 3. Ecroprocta

Sub-class II]. BRACHIOPODA

Order 1. EcarpINEs
Order 2. TESTICARDINES

THEIR SUBORDINATE GROUPS. 15

A few forms with a ciliated ven-
tral surface, These are consid-
ered by some as forming an inde-
pendent sub-class, closely allied to
Rotifera. x Ichthydium,
.Minute forms, usually encased in
chitinous tubes or “‘ cells.’’ Gen-
erally colonial, and then often
bearing a superficial resemblance
to a hydroid oranalga, Intestine
U-shaped; mouth surrounded by a
ridge (ophophore) bearing ciliated
tentacles.

Worm-like forms, enclosed ir
leathery tubes. One genus, Pho-
ronts.

Anus included within the lopho-

phore. Tentacles only partially
retractile. All marine.

x Ornatella, Loxosoma.
Anus outside the lophophore.

Tentacles completely retractile. A
few fresh-water forms, the rest
marine. x Bugula, Plumatella.
All marine, depressed in form,
with dorsal and ventral shells which
are symmetrical, but unequal.
Mouth situated between two spiral
ciliated arms, which lie coiled
up in the shell. A large fossil
order. Few living.
Shell without a hinge. x Lingudla.
Shell with hinge; usually calcare-
ous loops to support arms.

x Terebratulina.

16 A SYNOPSIS OF ANIMAL CLASSIFICATION.

TYPE IV. MOLLUSCA.

Soft-bodied, unsegmented animals, consisting typically of three
parts: head, foot, and visceral sac; this latter part is covered dorsally
by a duplicature of integument called the mantle, the outer layer of
which usually secretes a calcareous shell, consisting of one, two, or
several separate pieces, which sometimes depart from the original
bilateral symmetry; a complicated vascular system with a pulsating
heart and typically one or more pairs of plumose gills, the ctenidia,
which may be variously modified or entirely replaced by other organs;
nervous system composed of several pairs of ganglia; body cavity
restricted to a small open space surrounding the heart.

Class J. AMPHINEURA.......... A small group of bilaterally sym-
metrical molluscs showing similar-
ity to the Zurbellaria, They have
a nerve-ring around the mouth and
four parallel longitudinal nerve-
cords connected by transverse com-

missures.
Order 1. SOLENOGASTRES....... Mantle and shell wanting. Body
worm-like. x Proneomenia.
Order 2. CHITONES........... With a dorsal shell composed of

eight transverse pieces,

x Chiton.
Class II, PELECYPODA (Lamelli-

branchiata)............-...... Bilaterally symmetrical, or, in a
few cases, secondarily distorted,
owing to an habitual lateral posi-
tion; two lateral shells, usually
united dorsally. The single pair of
ctenidia seldom appears in a sim-
ple form, in most cases the separate
plates are elongated and filiform,
and are often doubled upon
themselves and united together in
such a way as to form two thin
lamella upon each side. They

I. TYPES IN DETAIL WITH THEIR SUBORDINATE GROUPS. 17

are without a distinct head and
lack a ‘‘ lingual ribbon’’ or ra-
dula, The foot is compressed and
never forms a creeping disc.

Order 1, PROTOBRANCHIA...... With normal, doubly pinnate
ctenidia extending backwards in
the mantle cavity, and free, ex-
cept at the base.

x Nucula, Foldia.

Order 2, FILIBRANCHIA........ Separate plates of the ctenidia
filiform and greatly lengthened,
and folded back upon themselves,
The separate filaments are free from
one another, but are so closely
approximated that they give the
appearance of continuous plates,

x Mytilus, Arca.

Order 3. PsEUDOLAMELLIBRAN-

GHTAL hid aus bud Sevicuavacelen wena das Similar to the last, but with slight
adhesions between the separate
filaments, caused by ciliated sur-
faces; also with a few cross-bars,
with vascular connexion between
the descending and ascending limbs
of each filament and with a vertical
folding or crimping of the lamelle
as a whole, forming ridges and de-
pressions. x Pecten, Ostrea.

Order 4, EvLaMELLiprancuia...Filaments so completely fused as
to be no longer recognizable as
such, and with the descending and
ascending lamellz thus formed so
frequently united by their adjacent
surfaces that the entire ctenidium
of one side appears in the form
of two gill-plates, a characteristic
once used as typical of the class

18

Order 5. SEPTIBRANCHIA

The following somewhat older
based upon the presence or absen

A SYNOPSIS OF ANIMAL CLASSIFICATION.

(‘‘ Lamellibranchiaia’’), The great
majority of the Pelecypoda are
here included. x Mya, Venus,
Ctenidia reduced to muscular par-
titions perforated by rows of gill
slits and dividing the mantle cavity
into two compartments,

x Silenia,

classification of the Pelecyfoda was
ce of a siphon and the conditions of

the adductor muscles, a system which had the advantage of being appli-
cable to the shells from which the soft parts have been removed, but
which is not so fundamental morphologically as the present one.

Order 1. SIPHONIATA

Sub-order 1. SINUPALLIATA....

Sub-order 2. INTEGRIPALLIATA..

Sub-order 2, HETEROMYARIA...

Sub-order 3. MONOMYARIA

Class III. SCAPHOPODA.

Class IV. GASTEROPODA

With two posterior siphons, separate

or fused. Edges of mantle often
joined.

Siphons long and contractile. Pal-
lial line with sinus.

x Mya, Venus, Solen.

Siphons short, not contractile. No

pallial sinus. x Cyclas.
Siphons absent,

Anterior and posterior adductor
muscles about equal. x Uxzo.
Anterior adductor very small.

x Mytilus.

Anterior adductor wanting.

x Ostrea, Pecten.

Bilaterally symmetrical molluscs
with visceral sac greatly elongated
in a _ dorso-ventral direction.
Mantle and shell tubular and
somewhat curved, with a smaller
dorsal and a larger ventral open-
ing. Ctenidia fail. Foot elon-
gated andconical. A single family
of marine forms. x Dentalium.
Molluscs with a head, foot, and
visceral sac. The first two are
bilateral; the third is generally
contained in a spirally twisted

Il. TYPES IN DETAIL WITH

Order 1. PROSOBRANCHIATA...

Order 2. HETEROPODA

Order 3. Putmonata

Order 4. PTEROPODA

ey

Order 5. OPISTHOBRANCHIATA. .

Class V. CEPHALOPODA

. Shell

THEIR SUBORDINATE GROUPS. 19

shell, usually capable of receiving
the other parts when retracted;
mouth furnished with a radula;
foot forming a creeping disc.
present; gill anterior to
heart; foot a creeping disc; sexes
separate.

x Oliva, Cyprea, Strombus.
Shell small or wanting; gill as in
previous order; anterior part of foot
compressed, forming a sort of keel;
sexes separate. This order in-
cludes a very few nearly transparent
forms, which swim on the surface
of the ocean. x Carinaria.
Land and fresh-water snails breath-
ing by plexus of blood-vessels
which lie in a respiratory chamber
communicating with the exterior,
and placed anterior to the heart;
shell generally present; hermaph-
troditic. x Helix, Limnea.
Shell fragile or wanting, foot de-
veloped into a pair of wing-like
expansions, hermaphroditic. A
small group of forms which swim
at night upon the surface of the
ocean. x Cymbuliopsis,

.Shell, when present, rather deli-

cate, often wanting; gill placed
behind heart; back of naked forms
often ornamented with simple or
dendritic papillae; hermaphroditic.

x Bulla, Eolts.
Head well developed, distinct from
body and with two large eyes;
mouth surrounded by many arms

20 A SYNOPSIS OF ANIMAL CLASSIFICATION.

or tentacles; foot rolled into a
sort of funnel.

Order 1. DIBRANCHIATA....... Gills two; eight or ten arms
around the mouth, covered with
cup-shaped sucking discs; ink-bag
present; shell internal (in Argo-
naufa not entirely covered).

x Loligo, Octopus.

Order 2. TETRABRANCHIATA....Gills four, mouth surrounded by
numerous unarmed tentacles; ink-
bag wanting; a heavy external
shell divided into chambers. A
single living genus. x Nautilus.

The present Cephalopods are the few degenerate descendants of a
very large and abundant group, which filled the seas in Palzeozoic and
Mesozoic times. They possessed, originally, well-developed shells,
divided into chambers; some shells being straight, others spirally coiled.
The Tetrabranch, Vauizlus, is the only living representative of the great
Order NAUTILOIDEA, and still retains a heavy chambered shell. The
other great Tetrabranch Order, the AMMONOIDEA, is entirely extinct.
These possessed spirally wound shells with chambers and septa, the latter
often fluted and otherwise ornate. The BELEMNOIDEA were Dibranchs.
They possessed usually straight shells, and were the ancestors of the
modern squid.

TYPE V. ARTICULATA.

Segmented bilateral animals, with a chitinous exo-skeleton which
varies in thickness from a thin skin to a hard shell, reinforced by
mineral salts. Body cavity present and spacious; alimentary canal
complete, approximately coinciding with the longitudinal axis; nerv-
ous system a double chain of ganglia, typically a pair for each
somite; vascular system consists of a longitudinal dorsal vessel, and
generally one or more ventral ones, connecting with the dorsal one
by commissures. Sexes almost always separate.

Sub-type I. ANNELIDES........Primitive Articulates, worm-like
in appearance and without jointed
limbs or definite somite-complexes.
Body cavity divided by dissepi-
ments into somitic divisions.

Il, TYPES IN DETAIL WITH THEIR SUBORDINATE GROUPS. 21

Class J. CHATOPODA........... Typical Annelids, with well-
marked external somites, cor-
responding to the internal meta-
merism; somites furnished with
paired groups of chitinous bristles.

Order 1. PoLycHzTA..........- Bristles conspicuous, situated on
raised lateral portions, the para-
podia, Head generally present.

x Nereis, Serpula,

Order 2. OLIGOCHETA......... Bristles very small, sunk in hol-
lows along the sides; no parapodia;
no distinct head; hermaphroditic.

x Nais, Lumbricus.

Class I]. HIRUDINEA.. ........ Aquatic hermaphroditic ecto-para-
sites; segments without bristles;
move by terminal, adhesive suck-
ers. External and internal seg-
ments do not correspond.

Order 1, RHYNCHOBDELLIDZ....Pharynx extensile, forming a sort
of proboscis, x Clepsine.

Order 2. GNATHOBDELLIDZ ....Pharynx not extensile, with three
longitudinal ridges which are often
toothed. x Atrudo.

SUPPLEMENTARY CLASSES (PROBABLY RELATED TO ANNELIDS).

Class CHATIFERA, formerly taken with Sipunculoidea to form Class
Gephyrea. Here belong a very few marine worms, Echzurus, Bonellia,
etc., which show affinities to the Chettopoda. They are segmented only
as larve, but possess paired nephridia and a system of blood-vessels
similar to that of Annelids.

Class SIPUNCULOIDEA includes a very few forms of marine worms,
bearing some slight affinity to Annelids. They were formerly united
with Cheetifera to form the class Gephyrea. They are cylindrical, unseg-
mented forms without bristles, and possess a retractile proboscis.

x Sipunculus, Phascolosoma,

Class CHETOGNATHA. This includes one form, Sagztfa, a small,
transparent, unsegmented worm found on the surface of the ocean. The
body is flat and possesses lateral fin-like extensions. The mouth is
armed with jaws beset with sharp hooks. Hermaphroditic. It develops
lateral coelom sacks, which appear to have the value of a metaccelom.
It is placed by some with the Nematodes. [Cf. p. 14.]

22

Sub-type II. ARTHROPODA. ..

Class I. CRUSTACEA...

Sub-class I. ENTOMOSTRAKA

Order 1. PuyLtLopopa

Order 2. CLADOCERA

Order 3. CopEpopa

A SYNOPSIS OF ANIMAL CLASSIFICATION.

More specialized Articulates with
jointed appendages (meropodia) and
with somites grouped to form three
somite-complexes, head, thorax,
and abdomen. These may be dis-
tinct or fused, either as cephalo-
thorax and abdomen or as a single
piece. Internally the cavities of
the somites are confluent, without
dissepiments.

Aquatic Arthropods, with two
pairs of antennze and numerous
pairs of appendages, usually show-
ing much differentiation. Respira-
tion either through the general sur-
face of the body or by localized
thin places, in the form of plates
or dendritic structures, upon or
near some of the appendages, A
few are secondarily adapted to a
terrestrial life.

Small, often minute Crustacea with
a variable number of somites,
Abdomen generally without ap-
pendages.

Numerous (10-40) pairs of flat-
tened, leaf-like legs, bearing sac-
shaped gills. x Branchipus.
Body enclosed in lateral integu-
mental duplicatures, forming a two-
valved shell which usually covers
thoracic and abdominal regions,
but leaves the head free. Second
pair of antennz enormously devel-
oped and used as oar-like organs
of locomotion. x Daphnia.
Body generally elongated and with-

I TYPES IN DETAIL WITH THEIR SUBORDINATE GROUPS. 23

Order 4. Ostracopa

Order 5. CIRRIPEDIA

Sub-class I]. MALAKOSTRAKA....

out integumental duplicature.
Four to five pairs of flattened,
two-branched legs used as oars.
Eggs carried in two lateral sacs on
the sides of the abdomen. Many
forms reduced by parasitism.

x Cyclops, Lernea, Argulus.
Body, including head, enclosed in
a bivalve shell, with hinge and ad-
ductor muscle. Seven pairs of ap-
pendages, of which only 2 (or 3)
may be reckoned as legs.

x Cypris.
Free-swimming only when young.
Adults become sessile and are
enclosed in an inverted position
in a calcareous two-valved shell.
Generally six pairs of two-
branched legs, modified to form
delicate many-jointed czrrz.

x Lepas, Balanus, Sacculina.
Generally large forms with a con-
stant number of somites (20), con-
sisting of a head with five, a thorax
with eight, and an abdomen with
seven somites. The first two por-
tions are often fused to form a
cephalo-thorax of thirteen somites,
Only the first six abdominal so-
mites bear appendages, and of
these the last pair is generally
modified and united with the ter-
minal somite to form a caudal
appendage. The paired repro-
ductive orifices of the male are
found upon the last thoracic legs,
near the base, and those of the

24 A SYNOPSIS OF ANIMAL CLASSIFICATION.

female upon the third from the
last.

The numerous Orders inciuded under this sub-class are arranged
for convenience into larger groups, which may be designated as “ super-
orders” or ‘‘legions,”’ and which facilitate the classification.

Super-order 1. LEPTOSTRAKA
(with a single Order)
Order 1, PHYLLOCARIDA......

.This group, mostly fossil, con-
tains but a single living form,
valuable as a link between Ento-
mostraka and Malakostraka. A
small integumental duplicature
covers the head and thorax. The
abdomen is 8-jointed, thus depart-
ing from the constant number
otherwise found in Malakostraka,
The feet are like those of phyllo-

pods.
x Nebalia.

Super-order 2. ARTHROSTRAKA. .Sessile-eyed Malakostraka, with

Order 1. AMPHIPODA..........

Order 2. Isopopa

free thoracic segments, and with-
out carapace. Thoracic append-
ages distributed as one pair of
maxillipeds and seven pairs of legs.
Brood cavity borne between tho-
racic legs.
Compressed forms, body generally
bent into a curve. Seven free
thoracic somites. Gills upon the
thoracic legs. Abdomen with six
pairs of legs, of which the first
three are used in swimming and the
last three form a springing or leap-
ing organ. In a few forms the
abdomen is reduced.

x Gammarus, Caprella.
Depressed forms with seven free
thoracic somites. The abdominal
appendages are in the form of

i. TYPES IN DETAIL WITH THEIR SUBORDINATE GROUPS. 25

flattened plates and protect the
gills, which are placed upon
them, Some are reduced, parasitic
forms.

x Asellus, Porcellio,

Super-order 3. THORAKOSTRAKA..Eyes situated upon movable
stalks. Carapace involving all or
nearly all the thoracic rings.
Brood cavity upon the ventral
side of the flexible abdomen and
protected by the sixth abdominal
appendage and the terminal seg-
ment (telson).

Order 1. CUMACEA..........-. Carapace small, involving only 3-4
thoracic somites, two pairs of
maxillipeds, and six pairs of legs.
Abdomen of female without ap-
pendages; of male with 3-2.

x Diastylis.

Order 2. STOMATOPODA........ Carapace involving five thoracic
somites, five pairs of maxillipeds,
and three pairs oflegs. Gills upon
the abdominal appendages.

x Sguilla,

Order 3. SCHIZOPODA.......... Carapace involving entire thorax,
eight pairs of two-branched, gill-
bearing, thoracic legs. No maxil-
lipeds.

x Aysts.

Order 4. DEKAPODA.......... Carapace large and heavy, involv-
ing the entire thorax, three pairs
of maxillipeds, and five pairs of
legs, of which the first bears
heavy claws. Gills at base of
thoracic feet upon the sides, pro-
tected by the edge of the carapace,

x Homarus, Cancer.

26 A SYNOPSIS OF ANIMAL CLASSIFICATION.

SUPPLEMENTARY CLASS, TRILOBITEA.

An important group of fossil forms, presenting some superficial
resemblance to the Isopods. They are oval and flattened in form, and
possess a dorsal carapace, divided by two longitudinal grooves into three
areas, one median (rhachzs) and two lateral (p/eure). The carapace
consists of a cephalo-thorax, behind which are a varying number of
freely movable somites sometimes called the “ ¢horax,” and terminated
by a plate-like “ Aygzdzum,” formed of several fused somites.

The ventral side is almost unknown. Probably each thoracic somite
had a pair of crustacean-like legs, above which there may have been a
pair of gills, protected by the overhanging edge of the carapace. Recently
(1894) some finely preserved specimens have been discovered showing
one pair of long antenne.

The Trilobites appear to have close affinity to the branchiate Arach-
noids, as well as to the genuine Crustacea.

Class II. TRACHEATA.......... Terrestrial Arthropods, with one
pair of antenne; appendages
numerous in the lower members
of the class; in the higher ones
few and definite in number. Res-
piration by means of branching
tracheal tubes opening to the ex-
terior by means of spiracles, placed
along the sides of the body. A few
are secondarily adapted for aquatic
life, and breathe by numerous de-
vices, mostly modifications of the
tracheal system,

Sub-class I, PERIPATOIDEA....... A group consisting of a very few
tropical forms, isolated from one
another, and found in all conti-
nents. In many respects they are
more like Annelids than Arthro-
pods, and form an interesting con-
necting link between the former
and the genuine Zracheata. The
body somites are all alike and the
appendages, which are creased or
folded rather than jointed, show
no regional differentiation. Each
somite has a pair of nephridia,

I TYPES IN DETAIL WITH

Sub-class I]. MyrrapopA

Order 1, CHILOPODA

Order 2. DripLopopa

Sub-class III. Hexapopa (INSECTA).

THEIR SUBORDINATE GROUPS. 27

opening at the base of the legs.
Respiration is by tufts of tracheal
tubes proceeding from irregularly
distributed spiracles. There is
but one important genus, Perz-
patus.
Generalized Tracheata, with the
somites and appendages very sim-
ilar to one another; i.e., with little
regional differentiation. There is
a distinct head, bearing antenne,
mandibles, and two pairs of max-
illee.
Depressed in form; a single pair
of legs to each somite; mandibles
well developed, fitted for predace-
ous life; first pair of legs trans-
formed into a pair of biting jaws
furnished with poison glands. ¢.
x Lithobius, Scolopendra,
Usually cylindrical in form, with a
tendency to coil up when attacked ;
the primary somites coalesce in
pairs, thus giving an appearance
as though there were a double pair
of legs to each of the very numer-
ous somites. x Lulus.

Body divided into three distinct
regions or somite-complexes :
head, thorax, and abdomen; the
head bears four pairs of appendages:
antennz, mandibles, and two pairs
of maxille; a lost pair appears in
some embryos between antennze
and mandibles; the thorax bears
three pairs of legs and usually two
pairs of integumental folds used

28

Order 1.

Order 2.

Order 3.

Order 4.

Order 5.

A SYNOPSIS OF ANIMAL CLASSIFICATION.

THYSANURA..........

PSEUDONEUROPTERA ...

ORTHOPTERA ........

as wings; the abdomen consists
typically of eleven somites with
modified terminal appendages for
palpation and oviposition. The
higher insects have gained second-
ary larval forms and thus develop
by a metamorphosis.
Minute wingless forms, with biting
mouth parts, found in decayed
wood and damp earth. They are
the most primitive insects and have
never developed wings. Some
show rudiments of abdominal legs.
Ametabolic; i.e., development di-
rect. x Podura.
Mouth parts biting, wings all alike,
transparent, delicate, with lace-
like venation. This group was
formerly united with the Neuro-
ptera, but has an active pupa
(hemimetabolism).

x Libellula, Ephemera.
Mouth parts biting, upper wings
parchment-like, generally narrow,
under wings membranous and
often folded. Development hemi-
metabolic; i.e., pupa active.

x Caloptenus.

NEUROPTERA......... Mouth parts biting, somewhat

modified in Phryganide. Wings
as in Order 2. Development
holometabolic; i.e., pupa quies-
cent. x Phryganea.

COLEOPTERA......... Mouth parts biting, upper wings

(elytra) forming hard shields for
the protection of the membra-
nous lower ones. Holometabolic.

I. TYPES IN DETAIL WITH THEIR SUBORDINATE GROUPS. 29

Thorax free and quite distinct from
the posterior portion, thus dividing
the body into three regions: head,
pro-thorax, and meso- and meta-
thorax + abdomen. Holometa-
bolic. x Carabus.

Order 6. Ruyncnota (HeEmip-

Order 7. LEPIDOPTERA.

Order 8. Direrera.....

Order 9. Hymenoptera

Mouth parts modified to form a
straight jointed beak, which lies
between the coxal joints of the
legs. Wings either membranous
and alike or with the outer diag-
onal half of the upper wings per-
gamenteous. Many forms wing-
less. Hemimetabolic.
x Coreus, Cicada.
Mouth parts a double-coiled pro-
boscis, formed by the first maxillz.
Wings alike in texture, membra-
nous, covered with minute colored
scales. Holometabolic,
x Papilio, Sphinx.
Mouth parts variously modified,
sucking, piercing, or lapping—
never biting. Fore wings mem-
branous, hind wings reduced to
minute knobs—the so-called bal-
ancers. Holometabolic.
x Culex, Musca,
Mouth parts biting, or biting and
lapping; wings membranous, alike
in texture, but hind pair reduced
in size; body generally much con-
stricted between thorax and abdo.
men. Ovipositor of female gen-
erally accompanied by organs for
sawing, boring, digging, or stinging,

3°

Class III. ARACHNOIDEA........

A SYNOPSIS OF ANIMAL CLASSIFICATION.

the latter modification equipped
with a.poison gland,

x Vespa, Formica,
Head and thorax fused into a
single piece, the cephalo-thorax,
bearing six pairs of appendages, of
which one is pre-oral. These
may all be used as legs, or one or
more pieces may be chelate and
serve as mandibles or weapons of
defence. In the lower forms the
abdomen is elongated and seg-
mented and may bear appendages,
but in the higher forms it is con-
solidated and may even be fused
with the cephalo-thorax. Respi-
ratory organs originally lamellate
gills, developed as adjuncts of the
abdominal appendages. In the air-
breathing forms they may be modi-
fied and reduced in number, or even
replaced by a tracheal system,
probably not homologous with
that of insects.

Sub-class I, ARACHNOIDEA BRANCHIATA.. Mainly fossil forms, all ma-

Order 1. GIGANTOSTRAKA

Order 2. LimuLorpEa

er at

rine, gills lamellate, one pair of eyes
in side of cephalo-thorax, and one
pair of small ones anterior to these
near the middleline. Coxal joints
of the legs, or of some of them,
forming spiny plates used in mas-
tication.,
Fossil crab-like animals with long
extended abdomen, which may or
may not terminate in a spine.

x ELuryplerus, Plerygotus.
Mainly fossil, with three surviving

I. TYPES IN DETAIL WITH THEIR SUBORDINATE GROUPS. 31

species, the ‘‘ horse-shoe crabs.’’
These have a shortened abdomen,
consolidated into a single piece,
and bearing six plate-like append-
ages, of which all but the first bear
gills. The larve pass through a
so-called ‘‘trilobite’’ stage, in
which they greatly resemble the
extinct group of Trilobitea. V. su-
pra, p. 26. This circumstance sug-
gests a possible relationship be-
tween these groups. x Limulus.

Sub-class II, ARACHNOIDEA TRACHEATA. . Mostly terrestrial, breathing

Order 1. SCORPIONIDEA........

Order 2. PSEUDOSCORPIONIDEA. .

Order 3. PHALANGIDA

either by gill-plates enclosed in
pneumatic chambers, the so-called
‘‘lungs,’’ or by tracheal tubes re-
sembling those of insects. First
two pairs of appendages serve as
mouth parts, and are often chelate.
Last four pairs serve as legs.
Elongated forms, with a broad
prz-abdomen of seven somites and
a narrow tapering post-abdomen
or ‘‘ tail’’ composed of six somites
and ending in a poisonous spine.
Second pair of appendages enor-
mously developed and chelate.
Four pairs of ‘‘lungs.”’

x Scorpio.
Tiny animals found under bark (and
sometimes in houses) resembling
miniature scorpions, but without
the tail. They breathe by tracheal
tubes, | x Chelifer.
Entire body a shortened oval.
Reduced abdomen closely applied
to cephalo-thorax, but distinct and

32 A SYNOPSIS OF ANIMAL CLASSIFICATION.

Order 4. ARACHNIDA....

Order 5. ACARINA.. ........-.

consisting of six (rarely eight)
somites. Mandibles chelate. Legs
very long and attenuated. Tra-
cheal tubes with one pair of spira-
cles between thorax and abdomen.

x Letobunum, Phalangium.

..Abdomen unsegmented, swollen,

and attached to cephalo-thorax by
a stalk. Mandibles end in a
simple claw with poison gland.
Second pair of appendages leg-like,
modified in male. Two to three
pairs of spinnerets at end of abdo-
men. One to two pairs of ‘‘ lungs’”’
situated on abdomen. These may
be also connected with a system
of tracheal tubes.
x Epeira, Agalena.
Abdomen fused with cephalo-
thorax; body unsegmented; ap-
pendages about mouth often
modified to form a sucking tube;
respiration by tracheal tubes or
merely through integument; many
parasitic forms.
x Ixodes, Tyroglyphus.

There are several other Orders of Arachnozdea, but they are confined
to the Tropics and of interest mainly to specialists,

SUPPLEMENTARY ARTHROPOD GROUPS (doubtfully referred to the
Arachnoidea).

Pantapopa (PYCNOGONIDA)

Extremely attenuated marine forms
with long slender legs and body
of about the same diameter.
Cephalo-thorax of six segments, of
which the first are fused and possess

Il. TYPES IN DETAIL WITH THEIR SUBORDINATE GROUPS. 33

a beak at the anterior end. Ab-
domen much reduced. Seven
pairs of legs (or fewer), containing
the reproductive organs and diver-
ticula of the stomach. Special
respiratory organs wanting.
x Phoxichildium.
TARDIGRADA.... 00... cece ee eeee Minute fresh-water animals, known
as ‘‘ water bears,’’ with four pairs
of very short legs bearing hooks;
hermaphroditic, and without spe-
cial organs of circulation or respi-
ration. x Macrobiotus.
PENTASTOMIDEA (LiNGuATULINA). ..Worm-like parasites found in the
lungs and nasal cavities of reptiles
and mammals. They. resemble
Platyhelminthes, but their devel-
opment is like that of the Arach-
noidea. Legs reduced to two pairs
of hooks about the mouth.
x Pentastomum.

TYPE VI. ECHINODERMATA.

A type of marine animals which, in the larval stage, are bilateral
and pelagic, but which, after a short larval life, attain through a
singular metamorphosis a pentamerous radiate structure. The adults
are characterized by the presence of calcareous elements in their in-
tegument which show all degrees of development from that of minute,
scattered plates to a complete test or shell in which the separate
plates are large and in close contact with one another. Locomo-
tion is effected by a water-vascular (ambulacral) system which com-
municates with the exterior and contains sea-water.

Class I. HOLOTHUROIDEA....... Oval or vermiform Echinoderms
covered by a leathery integument
in which are imbedded minute cal-
careous plates and _ spicules,

34 A SYNOPSIS OF ANIMAL CLASSIFICATION.

Order 1. PEDATA....

Order 2. APpoDa.....

Class II, ASTEROIDEA

Order 1. ASTERIDEA.

Order 2, OPHIURIDEA.........

Class III. CRINOIDEA. .

Class IV. ECHINOIDEA

Around the mouth is a crown of
fringed, retractile tentacles. Lar-
val form the Auricularia.
Ambulacral feet present.

x Pentacta, Thyone.
Ambulacral feet wanting.

x Synapia.

Star-shaped to pentagonal Echino-
derms, with exo-skeleton in the
form of a rough net-work studded
with short fixed spines. Ambu-
lacral feet in grooves on oral side.
No definite boundary between disc
and arms; larval forms the Bzpin-
naria and Brachiolaria.
Disc and arms distinct, the latter
serpentine and very brittle. Lar-
val form a Plufeus, similar to that
of Class IV.
Sessile forms, somewhat resem-
bling Ophiuridea on stalks. The
part corresponding to the disc of
the latter is here called the calyx
and is so placed that the mouth is
above, surrounded by the many
branched arms, Larval form oval
in form, with ciliated bands run-
ning around it.
Spheroidal, oval, or disc-shaped
forms, with extensive exo-skeleton
composed of large calcareous plates
arranged in meridional rows, and
beset with movable spines. The
ambulacral feet project from foram-
ina in the plates of certain rows,
called ambulacral. Larval form
a Pluteus.

Il. TYPES IN DETAIL WITH THEIR SUBORDINATE GROUPS. 35

Order 1. ReGULARIA.......... Mouth and anus in the centre of
their respective surfaces.
x Arbacia, Toxopneustes.
Order 2. CLYPEASTROIDEA...... Mouth central, anus eccentric,
often near the outer margin.
x Echinarachnius,
Order 3. SPATANGOIDEA........ Mouth and anus both eccentric.
x Spatangus.
Aside from these classes there are two wholly fossil groups, often
reckoned as classes, the CYSTIDEA and the BLASTOIDEA. These seem
allied to the Crinoids. The CySTIDEA possessed irregular calyx plates

and some of them were without arms. The BLASTOIDEA were all arm-
less, but were regular in structure, with well-marked ambulacral areas.

TYPE VII. PREVERTEBRATA.

A group of apparently very dissimilar animals, all of which pos-
sess gill slits in the pharyngeal region, a dorsal nervous system and
a more or less well-defined endoskeletal rod, the notochord. They
are thus seen to be allied to the Vertebrates and undoubtedly repre-
sent the much-modified descendants of the transitional forms which
became the ancestors of that group.

Class 1. ENTEROPNEUSTA......Small, worm-like animals, with
habits similar to Annelids, and
found between tide-marks in mud
flats. At the anterior end is a
conical and flexible proboscis with
which the animal pushes its way
through the mud; this is followed
by the ‘‘ collar’’ at the upper ven-
tral edge of which is the mouth;
below this is a respiratory region,
perforated by pairs of gill-slits
which communicate with the pha-
rynx. Asmall dorsal diverticulum
at the anterior end of the pharynx
represents the notochord.

x Balanoglossus, Harrimama.

36 A SYNOPSIS OF ANIMAL CLASSIFICATION.

Cephalodtscus and Rhabdopleura, two sessile forms formerly classed
as Order, Pterobranchia, under Bryozoa, have been found to resemble
Balanoglossus. In young buds of the former a division into proboscis,
collar, and body may be seen. There is also a single pair of gill-slits, and
a dorsal diverticulum of the intestine (= notochord ?) lying under the
dorsal nervous system. In Rkaddofpleura no gill-slits have been detected,
but in other respects the structure is similar to Cephalodzscus.

Class II. TUNICATA.....

re reed

A group of marine animals which
are free-swimming during larval
life at least, and which possess an
endoskeletal rod (notochord) in
the tail. The body of the adult
is enclosed in a mantle or ‘‘ tunic,’’
which may be gelatinous, leathery
or cartilaginous, and possesses an
incurrent or oral and an excurrent
or anal orifice. The pharynx is
perforated by gill-slits which may
become so numerous as to convert
the entire pharyngeal wall into a
lattice-work. Many species are
sessile when adult and in these the
intestine becomes U-shaped and
the two mantle openings approxi-
mate one another, while in the
free-swimming forms the intestine
is straight and the two orifices are
situated at the ends. ;

Sub-class I. PERENNICHORDATA....Free-swimming forms, resembling

Sub-class II. AscIDIACEA

the larve of higher Tunicates.
They possess a long tail provided
with a skeletal axis, the notochord.
Pharynx with a single pair of gill-
slits. No definite mantle but a
gelatinous envelope.

x Appendicularia.
Body sac-like, with pharyngeal
wall completely perforated with

Il. TYPES IN DETAIL WITH THEIR SUBORDINATE GROUPS. 37

Order 1. Ascipizé.

Order 2. PyROSOMINE........

Sub-class III. THALIACEA........

Order 1. DoLioLi#...... Sees

Order 2. SaLPié,

gill-slits, The typical members of
this class are solitary and sessile,
with the two orifices approximated.
Some are colonial with certain
parts in common, and in a few of
these cases the colony is free-swim-
ming and pelagic.

Sessile forms, either solitary (mona-
scidie), or colonial (synascidie),
and arranged in generally stellate
groups, known as cenodia.

x Boltenia, Botryllus.
Free-swimming, transparent colo-
nies of a cylindrical or cone-
shaped form. Incurrent open-
ings upon the exterior, cloacal
openings in the interior.

x Pyrosoma.
Free-swimming, pelagic forms,
transparent and surrounded by a
gelatinous tunic. Pharynx with
either two rows of gill-slits or with
a single pair of large gill-slits.
Oral and cloacal openings at oppo-
site poles. The members of this
group often show a remarkable
alternation of solitary and colonial
generations, or even a still more
complicated development.

.Two rows of gill-slits. Muscle

bands in the form of closed rings.
Mantle thin. Generative cycle
complex, including one sexual and
two asexual generations.

x Doliolum.

..A single pair of gill-slits. Muscle

bands not in the form of complete

38 A SYNOPSIS OF ANIMAL CLASSIFICATION.

Class III. LEPTOCARDII

rings. Mantlethick. Alternation
of generations simple, solitary
asexual individuals alternating
with a chain-like series of sexual
forms. x Salpa.
This class contains a very few
closely allied animals, of which
Branchiostoma (= Amphioxus) is
the typical representative. The
body is fish-like, but without defi-
nite head, and pointed at both
ends. The notochord extends
through the entire body, from tip
to tip, just dorsal to the aliment-
ary canal. The pharynx is per-
forated by numerous pairs of lateral
gill-slits, which in the larva com-
municate directly with the exterior,
but which in the adult open into
a spacious peribranchial chamber
formed by folds of the integument
and communicating with the ex-
terior by means of a median ventral
opening, the atriopore, situated
posteriorly, but anterior to the
anus. The central nervous sys-
tem consists of a dorsal cord
lying upon the notochord. In
general plan of structure and the
relationship of the organs these
animals are essentially Vertebrate,
but they lack a definite head, and
are without skull or specially
differentiated brain.

x Branchiostoma.

Il. TYPES IN DETAIL WITH THEIR SUBORDINATE GROUPS. 39

TYPE VIII. VERTEBRATA.

Division I. CYCLOSTOMATA. . Vertebrates with a circular sucto-
rial mouth armed with chitinous
teeth; no jaws; 6-7 pairs of circu-
lar gill-openings.

Class. MARSIPOBRANCHIL....... The only class included here,
with characteristics of the Division.
Its two sub-divisions have the
value of Families, as follows:

Family 1. Pefromyzontide.....,Nasal cavity a median blind-sack.
(Lamprey eels. ) Mouth without tentacles. They
attach themselves by their circular
mouth to the sides of fishes and
suck their blood. Fresh-water
and marine forms.
x Petromyzon.
Family 2. Jlyximd@.......... Nasal sack provided with an inner
(Hag-fish. ) palatal opening. Mouth with
tentacles. Habits more parasitic
than the former. Thev push their
way even into the body-cavity of
other fish and consume their vis-
cera. All marine. x JLxine.

Division Il. GNATHOSTOMATA.. Vertebrates with mouth in the
form of a transverse cleit, sup-
ported by two jaws; teeth usually
present, composed of enamel and
dentine.

AANA ENA cetaxt coke Embryo without amnion or other
foetal membranes; some have
lungs, but all breathe by gills
during at least a portion of their
life; cold-blooded.

Super-class I. ICHTHYOPSIDA..A group equivalent in extent to
namnia q. t.

40

Class J. PISCES

Order 1. SzLacuit (ELasmoprancuit). .Skeleton

Order 2. GANoIDEI

ee

Cr

Order 3. Dipnor

Order 4. TELEOSTEI

eee econ

Class II. AMPHIBIA........ ieee

.Skeleton mainly osseous.

A SYNOPSIS OF ANIMAL CLASSIFICATION.

Aquatic Anamnia, with branchial

respiration. Paired limbs in the
form of fins (cchthyoplerygia).
Integument generally produces

scales, which contain bony ma-
terial produced by the corium.
Heart with one auricle and one
ventricle.

cartilaginous,
scales placotd, Tail heterocercal.
5-7 separate gill openings without
operculum,

x Squalus, Raja, Chimera.
Skeleton more or less reinforced
by bone. Scales typically rhom-
boid in form and with a hard pol-
ished surface (= ganoid). Tail
heterocercal. Gill-slits with oper-
culum. x Acipenser, Lepidosteus.
Skeleton mainly cartilaginous.
Notochord persistent. Paired fins
with a central skeletal axis and
with or without lateral rays.
Median fin continuous around tail.
Swimming-bladder functions as
lung. Gills with operculum. In
one species small external gills
also. A very small, but iso-
lated group, including 3-4 living
species.

x Ceratodus, Protopterus.
Scales
cycloid or ctenoid. Tail homo-
cercal. Gills provided with an
operculum.
Skin naked, very glandular and
slimy. Gills, external and inter-

il. TYPES IN DETAIL WITH THEIR SUBORDINATE GROUPS. 41

Order 1. Uropera

Order 2. GyMNOPHIONA

Order 3. ANURA

B. AMNIOTA

nal, present at some stage, gen-
erally transitory. Lungs usually
present, with larynx and trachea.
Paired limbs of the hand-form
(chetropterygium) with normally
five digits, often reduced in
number, Two occipital con-
dyles,

Mi et dditen tube Body elongated. Tail persistent.

In some of the lower members of
the group one or two gill-slits per-
sist throughout life, and in a few,
the external branchiz also persist.
Typically lungs are present in the
form of simple, attenuated sacs,
but in some cases they are wanting
and are functionally replaced by
a secondary respiratory organ
formed by the walls of oesophagus
and pharynx and worked by
muscles.

x Wecturus, Desmognathus.

Same bataserets Serpentine subterranean forms

without tail, limbs or gills. In-
tegument with minute scales
sunken in pits.

x Cecilia.

dp warren aks Compact, cephalized forms, with

tail present in larval life only.
Hind legs enormously developed
and used for leaping and swim-
ming. No gills when adult.

x Rana, Bufo, Hyla, Pipa.
Embryo enveloped in an amnion;
breathe by lungs and never by gills;
mainly terrestrial.

Super-class II. SAUROPSIDA....Skin thin and dry, covered with a

42 A SYNOPSIS OF ANIMAL CLASSIFICATION.

Class III. REPTILIA.

profusion of chitinous organs, often
of great complexity; embryo de-
veloped within an egg; a single
median occipital condyle.

i avlcvoncetar Yee eas Integument covered with scales,

horns, and other structures of epi-
dermic formation. Glands con-
fined to a definite locality (femoral
glands of lizards) or wanting.

The Orders of living reptiles are conveniently arranged under the
the two groups of Plagzotremata and Hydrosaurza, but if the fossil
Orders were included, this classification would require some amendment.

Group 1. PLAGIOTREMATA. .Cloacal opening transverse, behind

Order 1. LacERTILIA.........-

Order 2. OpHIpiIa

which, in the male, are paired
organs of copulation. Body uni-
formly covered by delicate scales,
which are cast off yearly, often as a
single piece. Habits mainly ter-
restrial and arboreal. Quadratum
movably articulated with skull (ex-
cept in Rhynchocephata, v. infra).
Four well-developed limbs in the
typical forms, and sternum or
shoulder girdle present in forms in
which the limbs are reduced.
Body very much attenuated, limbs
wanting, no rudiment of shoul-
der girdle or sternum. A single
lung developed (right). Other
paired organs placed the one be-
hind the other.

x Crotalus, Python,

A single species of a very ancient type of lizard occurs in New
Zealand Sphenodon (Hattena) punctata. The quadrate is immovable,
ventral ribs and abdominal sternum are present, the vertebrz are amphi-
ceelous. It is referred to the Order Rhynchocephatza,

II. TYPES IN DETAIL WITH THEIR SUBORDINATE GROUPS. 43

Group 2. HYDROSAURIA. ..Cloacal opening oval in shape, its
longer axis longitudinal. A single
organ of copulation in the male,
anterior to the cloaca. Scales
large and irregular, often reinforced
by bony plates, which may coalesce
to form dorsal and ventral shields.
Mainly aquatic in habits. Quad-
ratum immovably attached to
skull,

Order 3. CHELONIA........ ..Body enclosed by dorsal and ven-
tral shields, formed partly by ele-
ments of the endo-skeleton and
partly from the integument. Teeth
functionally replaced by horny
beak, with sharp cutting edge.

x Chrysemys, Chelone.

Order 4. CROCODILIA.......... Body elongated, covered by large
plates, which do not coalesce.
Thoracic and abdominal sterna
present, connected by ventral and
dorsal ribs. Teeth large, in alveoli.

x Alligator, Crocodilus.

Our knowledge of Reptilia is greatly increased by the discovery of
several important fossil Orders. The THEROMORPHA, very primitive in
some particulars, possessed certain anatomical characteristics which are
suggestive of the M/ammalza, and are thus considered by many as ances-
tors of the latter group. The Mosasauria, an Order of snake-like
marine reptiles, were allied to both Lacertdiza and Ophidza, and it is pos-
sible that surviving members of this group are occasionally seen and
called ‘‘sea-serpents.”

The PTEROSAURIA were allied to the Lacertilia, and possessed mem-
branous expansions of the integument of the arms and fingers, by which
they could fly. The PLEISIOSAURIA and ICHTHYOSAURIA were hydro-
saurs, the former somewhat resembling turtles, the latter, crocodiles.
The DINOSAURIA included some enormous terrestrial forms with mas-
sive skeletons, e.g., Brontosaurus and Jguanodon. Other smaller Dino-
saurs may have been the precursors of birds. They walked mainly upon
their hind feet, possessed pneumatic cavities in their bones, and showed
many other avian characteristics. An important form is Compsognathus,
which shows affinity to Archgopteryx (see introduction to Aves).

44 A SYNOPSIS OF ANIMAL CLASSIFICATION.

Class V. AVES*..... SSR aoed th Warm-blooded Vertebrates, show-
ing many reptilian characters, but
differing from them in the pos-
session of feathers, which are epi-
dermic structures closely related to
scales. The anterior limbs, modi-
fied to form wings, generally give
the animal the power of flight.
Quadrate bone movably articulated
with the skull. A single occipital
condyle.

The classification of this group which has obtained until recently,
and the one still found in the majority of text-books, is artificial in
character and results from an attempt to differentiate for convenience
the enormous number of living species which are too nearly alike mor-
phologically to sanction such a division. ‘‘The Order of birds is so
uniform in its structural features that it is difficult to find important
characters to differentiate the twelve thousand known species into con-
venient groups. As a result, ornithologists have raised the number of
minor groups into so-called Orders, which are scarcely of Family rank,
Hs we are to accept the rules in vogue in other groups of Vertebrates ”
(Kingsley).

Por convenience the lesser groups, usually described as Orders, are
here retained as Sub-orders, although hardly equivalent to such groups
elsewhere.

Sub-class I. SAURURZE.......... Jaws containing teeth, tail elon-
gated, vertebrated throughout, and
with a pair of contour feathers to
each vertebra; digits of the wings
not anchylosed, partially free, three
of them provided with claws. This
group rests upon the remains of a
single fossil species (two speci-
mens) from the Jurassic limestone
of Solenhofen, Germany.

x Archaeopteryx.
Notr.—The classification of birds as here given follows closely that of Kingsley
(Vertebrate Zodlogy, 1899) which, in its turn, is based upon the comparatively re-

cent investigations of Firbringer and others. The more familiar names for the
groups of carinate birds are added to Order 3. Euornithes, as its sub-divisions.

Il. TYPES IN DETAIL WITH THEIR SUBORDINATE GROUPS. 45

Sub-class II. QDONTORNITHES.,,..,

«‘ Toothed-birds,’’ a-group based
upon fossil, bird-like forms, found
in the cretaceous beds of Kansas
and Colorado. The remains repre-
resent two types, sufficiently dis-
tinct to constitute different orders.

Order 1. OponToHOLCH....... Ratite birds, with teeth in con-

tinuous alveolar grooves; halves of
mandible united by cartilage;
wings much reduced, containing
humerus alone; caudal vertebre
expanded and paddle-like. Feet
fitted for swimming.

x Hesperornis, Lestornis.

Order 2. ODONTORMA......... Carinate birds with teeth set in

separate sockets; halves of man-
dible united by cartilage. Wings
strong and powerful.

x Ichthyornis, Apatornis.

Sub-class II]. EURHIPIDURE...... This sub-class includes all living

Order 1. DROMMOGNATHI..

birds. They are toothless, with
two halves of the mandible anchy-
losed; a short tail ending in a
pygostyle of several fused vertebre.

. Running birds with rudimentary or

small wings and large, heavy legs.
An important anatomical character
is the dromeognathus skull, i.e.,
one in which the palatine bones
are separated from the rostrum by
a wide vomer. Feathers of the
down type (rami not united).
This Order includes the old group
of ‘‘ Ratiiae,’’ besides a few others,
extinct and recent, some being
carinate,

x Struthio, Apteryx, Tinamus.

46 A SYNOPSIS OF ANIMAL CLASSIFICATION.

Order 2. IMPENNES........... Aquatic birds with short, paddle-
like wings used only for swimming ;
no distinction of feathered and
featherless areas. Feathers cover-
ing wings scale-like; dorsal ver-
tebrz opisthoccelous and movable
upon one another; uncinate proc-
esses not anchylosed to ribs; the
three elements of the tarso-meta-
tareus incompletely fused, leaving
slit-like foramima, a peculiarity
possessed by no other living forms.

x Aptenodytes, Spheniscus.

Order 3. EvorNITHES........ Nearly all living birds belong here.
The sternum is carinate and the
wings well developed. The skin
possesses well-marked feathered
and featherless areas and the wings
and tail are furnished with contour
feathers.

x Anser, Aquila, Gallus, Passer.

The numerous sub-divisions of this Order, considered here for con-
venience as Sub-orders, may be grouped in three groups in accordance
with a fundamental anatomical characteristic, viz.: the relationship
existing between the maxillo-palatine processes and the vomer as seen
upon the ventral side of the skull. Thus, in the desmognathous type the
maxillo-palatine processes are united in the median line, forming a bony
roof to a part of the palate; while in the schizognathous and egithogna-
thous types the maxillo-palatine processes are separated from each other,
leaving a median, longitudinal cleft in the bony palate. These two last
types are distinguished from each other by the shape of the anterior
end of the vomer, which is pointed in the Schzzoguathe and broad and
notched in the 4gzthognathe.

The groups and their sub-divisions are arranged as follows:

Group A. Desmognathe.

Sub-order 1. Steganopodes..... x Pelicanus.
Sub-order 2. Lamellirostres..... x Anser, Cygnus, Anas.
Sub-order 3. Herodiones....... x Ardea, Ibis, Ciconia.
Sub-order 4. Rapfores......... x Aguila, Strix.
Sub-order 5. Coccygomorphe .. x Cuculus, Halcyon.

Sub-order 6. Psti#fact. ....... : x Psittacus, Cacatua, Conurus,

Il, TYPES IN DETAIL WITH THEIR SUBORDINATE GROUPS. 47

Group B. Schizognathae.

Sub-order 7. Cecomorphe....
Sub-order 8. Zurbtnares......
Sub-order 9. Grall@........
Sub-order 10. Galhng........
Sub-order 11. Columbea.......
Sub-order 12. TZrochilide......
Sub-order 13. Prcz...........
Group C. Agithognathe........

Sub-order 14. Passeres........

Super-class I. MAMMALIA ...
Class VI. MAMMALIA

Sub-class I. PROTOTHERIA

Order 1. MonoTREMATA,

Two extinct Orders of Prototheria have been established.

x Podiceps, Alca, Larus, Sterna,
x Diomedea, Fulmarus.

x Grus, Charadrius, Scolopax.
x Gallus, Perdix.

x Columba, Didus.

x Trochilus, Lophornis.

x Picus, Colaptes.

(Over half the known species of
birds belong here.)

x Passer, Tyrannus, Hirundo, Pa-
radisea, Corvus,

.Same as class: Mammalia. g. v.

Warm-blooded vertebrates. Body
clothed with hair; young nourished
by milk, a secretion of integu-
mental glands. Quadrate in mid-
dle ear, two occipital condyles.

Low oviparous mammalia with rep-

tilian characteristics, such as an
episternum and well developed

coracoids. The young, immature
when hatched, are brooded either
in a nest or in a brood pouch tem-
porarily developed. No localized
mammary glands or nipples; but
the integument of the mammary
pocket is lactiferous. Alimentary
canal, urethra, and reproductive
ducts open into a common cloaca.
With characteristics of the Sub-
class, Ornithorhynchus, Echidna,

The

Protodonta, represented by lower jaws of two Jurassic species, and the
Multttuberculata, represented by several genera founded upon numerous

teeth from the Upper Jurassic and

Lower Eocene. The separation of

these Orders rests upon dental characteristics.

48 A SYNOPSIS OF ANIMAL CLASSIFICATION.

Sub-class II. EUTHERIA........

-Cloaca divided transversely into

intestinal and genito-urinary tracts;
mamme furnished with nipples;
viviparous, early development takes
place in uterus; no episternum;
coracoid reduced and fused with
scapula in adult.

Group A. Marsupialia (Didelphia).. Division of cloaca seldom

Order 1. PoLyPROTODONTIA....

Order 2. DrproroponTia......

complete. Young are born in an
immature condition and sheltered
in an external integumental pouch
(marsupium) on the ventral surface
of the abdomen; two lateral uteri
and vaginz, sometimes incom-
pletely united.

.More than three incisors on each

half of upper jaw.
x Didelphys, Perameles.

.Three incisors, or less, on each

half of upper jaw.
x Macropus, Phascolomys.

Group B. Placentalia (Monodelphia) . . Young nourished in uterus

Order 3. EDENTATA..........

Order 4. SIRENIA...........

of mother by a capillary mass, the
placenta, which adheres to the
uterine wall and is connected with
the embryo by the umbilical cord.
Anus separated from the uro-genital
sinus by a perineum.

.Teeth either wanting or in con-

dition of retrogressive metamor-
phosis. Incisors and canines gen-
erally fail. Large number of sacral
vertebree. Placenta indeciduate,
diffuse, or occasionally discoidal.
x Dasypus.

.Aquatic forms with only the ante-

tior limbs developed. Teeth often

Hl. TYPES IN DETAIL WITH

Order 5. CETACEA...........

Order 6. ARTIODACTYLA.......

Order 7, PERISSODACTYLA.....

Order 8. Proposcrpia........

THEIR SUBORDINATE GROUPS. 49

wanting; molars, when present, re-
semble those of ungulates. Sparsely
hairy. A single pair of pectoral
mammary glands. Placenta in-
deciduate, diffuse. x Manatus.
. Aquatic forms with naked skin, pro-
vided with hair in embryo. Hind
limbs fail externally; rudiments
under skin. Mammary glands in
folds on the sides of the vagina,
External nares in top of head con-
necting directly with a tubular pro-
longation of the larynx. Placenta
indeciduate, diffuse. x Balena,
-Hoofed mammals with an even
number of toes, of which two (3
and 4) are the best developed, re-
sulting typically in the cloven hoof.
The pre-molars, 3-4, are smaller
than the molars. Many members
of this Order are ruminants. Pla-
centa indeciduate, cotyledonal in
most ruminants, in other cases dif-
fuse. x Bos, Hippopotamus,
-Hoofed mammals with an odd
number of toes, five, three or one,
the middle one being the best de-
veloped. Prze-molars equal the
molars in size. Integument often
very thick. Placenta indeciduate,
diffuse. x Rhinoceros, Equus.
.A group allied to the two previous
Orders, but with five stout toes
furnished with hoofs, making a
ponderous rounded foot. The
snout is enormously prolonged,
forming a muscular proboscis

50 A SYNOPSIS OF ANIMAL CLASSIFICATION.

Order 9. Hyracorpga. .

Order 10. CARNIVORA. .

eee

tipped with a sensitive finger-like
process. One pair of incisors,
which develop into mammoth
tusks. (In recent forms it is those
of the upper jaw. Lower incisors
in Dinothertum.) Placenta decidu-
ate and zonary. x Llephas.

..A single family of small, rodent-

like mammals with five digits on
fore foot (two rudimentary) and
three on hind foot. Four upper
and four lower incisors, outer up-
per ones early deciduous, leaving
inner ones, which are chisel-like and
continue growth as in Rodentia.
Placenta deciduate and zonary.

F x Hyrax.
Beasts of prey with sharp well
developed canines and pointed
molars. The toes are armed with
claws, which may become sharp
and retractile. Placenta deciduate
and zonary. There are two groups,
one terrestrial, /7ssipedia, with toes
separate, and one aquatic, Pinnipe-
dia, with toes strongly webbed,
forming paddles. x Felis, Phoca.

Order 11, RopEnTIA.......... A group of small animals with

Order 12. INSECTIVORA

teeth fitted for gnawing. One pair
of incisors in each jaw develop
into sharp cutting chisels; the
others are usually wanting. Ca-
nines wanting. The molars are
fitted with transverse ridges for
cutting. Placenta deciduate and
discoidal. x Mus, Scturus.
Small insect-eating mammals with

Il. TYPES IN DETAIL WITH THEIR SUBORDINATE GROUPS. 51

Order 13. CHEIROPTERA......

Order 14. Prosrui....

Order 15. PRImaTES..........

Sub-order 1. Platyrrhin?......

Sub-order 2. Catarrhint

the teeth prolonged into sharp

points. Canines small or wanting.

Placenta deciduate and discoidal.
x Zalpa,

.The only flying mammals. Toes

of anterior limb exceedingly attenu-
ated, thus forming a framework
for a thin leathery web, which also
includes the hind limb and tail.
Thumb of fore limb and all the
hind toes free. Teeth pointed as
in Jnsectivora. In many respects
similar to the next Order. Pla-
centa deciduate and discoidal.

x Vesperhtio.

.A group of animals closely allied

to the apes, but of a generally
lower structure. Appendages
hand-like, with opposing thumbs,
but with a double uterus, and a
diffuse though deciduate pla-
centa. The nails are developed
into claws. x Lemur, Tarsius.
Toes with flat nails. Appendages
more or less hand-like, and gen-
erally fitted with opposing thumbs
for grasping. One pair of pectoral
mammary glands. Placenta de-
ciduate and discoidal.

Nose flattened, nostrils separated
by a broad septum, so that their
orifices look outward. Natives of
the Western Hemisphere. x Cebus.
Internasal septum thin. Nostrils
look forwards and downwards.
Natives of the Easten Hemi-
sphere. x Cercopithecus, Gorilla,

52 A SYNOPSIS OF ANIMAL CLASSIFICATION.

Sub-order 3. Amthropint...... Nose as in Sub-order 2, Thumb
more movable—great toe less so.
Hairreduced. Erect position nor-
mal. x Pithecanthropus, Homo.

Ill. ARTIFICIAL KEY FOR THE DETERMINATION OF
SPECIMENS.

I. Entire animal consists of a single cell, though occasionally with
more than one nucleus; either independent or arranged in the
form: of 2, colony. is 4sasea% va rwwae see ys eee es sees Protozoa.

II. Animal multicellular, usually “of an appreciable size; when
minute, then almost always with certain definite organs, such
as an intestinal canal, ciliated bands, paired limbs, etc.

A. Structure radiate.
1, Parts in 2s, 48, 6s, ete.

(2) Nettle-cells for defense, placed upon tentacles
or other exposed parts; both free-swimming
transparent forms (‘‘ medus@’’) and sessile,
vase-shaped forms (‘‘polyps’’), the latter
usually colonial. Apical (= ab-oral) pole
non-sensitive, serving in sessile forms as
place of attachment............. Cnidaria.

(4) Free-swimming, transparent, pelagic forms,
with eight meridional rows of swimming-
paddles. Apical pole furnished with sense-
OTZANS ss ease dew ewe ees eae e's Ctenophora.

Qs Parts in 5Si:dseaseecdaa si xwae ae Echinodermata.
3. Parts not in a definite number, but animal more or
less vase-shaped or cylindrical and with an apical
excurrent opening, and minute incurrent pores
along the sides; no tentacles; walls usually thick
and their substance filled with a skeletal support
of either spicules or of horn threads... .Porifera.
B. Structure bilateral, or nearly so.
1. Body externally segmented (or apparently so).
53

54 Il. ARTIFICIAL KEY FOR THE

(2) Appendages consist of fleshy, jointless lobes,
beset with bristles; or else of the bristles
alone, arranged in paired lateral groups.

Annelides.

(4) Appendages jointed, and usually differentiated
into various sorts of limbs, with different
functions.............0000 eee Arthropoda.

(c) Appendages none; suckers at ends of body,
which is flat and very finely segmented.

Hirudinea, sub Annelides,

(d) Appendages none; body composed of ‘‘ links ’’
which increase in length posteriorly, and
which have the appearance of somites; geni-
tal pores on edges of links; anterior end
head-like, but with no mouth; usually
equipped with hooks and suckers.

Cestodes, sub Vermes.

2. Body segmentation not really external, but marked
in the muscular system in the form of V-shaped
lines which are seen through the transparent skin.

No head, but pointed at both ends,

Amphioxus, sub Prevertebrata.

3. Body segmentation not apparent externally, but
marked in the muscles of the trunk and in the
trunk portions of the internal skeleton; two pairs

of paired limbs, one or both of which may be

PEMUCEO iio io oie ein ais ee Hed suse ees es Vertebrata.

4. Body unsegmented (at least apparently so).

(2) Colonial, i.e. animals in groups, with organic
connection between them or between their
skeletal supporting structure. All aquatic.

* Sessile, aquatic.

{ Each animal in a ‘‘cell’’ into
which it may be withdrawn;
ciliated tentacles around the
mouth. Marine and in fresh
water....Bryozoa, sub Vermes.

‘

DETERMINATION OF SPECIMENS. 55

tt Animals bag-shaped, with in-
current and excurrent orifices,
of which the latter may be held
in common by the colony.
Arrangement of animals in
rows, rosettes, bunches, etc.
All marine.

Ascidiacea, sub Prevertebrata.
** Free-swimming, all marine.

}{ Colonies cylindrical or conical,
with one end open; separate
animals tubular, with an open-
ing at either end.

Ascidiacea, sub Prevertebrata.

Tt Colonies chain-like, in single or
double rows; separate animals
cask-shaped, with zone-like
bands; transparent.

Thaliacea, sub Prevertebrata.
(2) Solitary, or, if associated, without organic con-
tinuity.
* Sessile, aquatic.

+ With two calcareous shells, dorsal
and ventral. Two spiral, cili-
ated arms supported by skele-
ton within the shell.

Brachiopoda, sub Vermes,

Tt With calcareous shells, but not
as above and without the spiral
arms........ Some Mollusca,

ttt Microscopic forms in tubes.
Ciliated lobes at free end.

Rotifera, sub Vermes.

tttt Bag-shaped, either with or

without a stem; two openings,
incurrent and excurrent.

Ascidiacea, sub Prevertebrata.

56 Il, ARTIFICIAL KEY FOR THE

**® Locomotive, or at least unattached.
} Body worm-like, round or flat.

No shell.

fT Body cylindrical, usually
pointed at the anterior
end; mostly parasitic.

Nematelminthes, sub
Vermes.

Tt Body flattened and capable
of considerable elongation
and contraction; mostly
parasites.

Platyhelminthes, sub
Vermes.

Tit Anterior portion cylindri-
cal, succeeded by a nar-
row zone, the “‘ collar.
Posterior portion some-
what flattened, live in
burrows in sand of sea-
coast.

Enteropneusta, sub Pre-
vertebrata.
+t Body not worm-like.

f Body soft and slimy, covered
dorsally by an integu-
mental duplicature, the
mantle, which usually se-
cretes a shell; marine,
fresh-water, and terrestrial
forms,
er eee Mollusca.

ft Pelagic, transparent forms;
cask-shaped and with
zone-like bands.
Thaliacea, sub Preverte-

brata.

ce)

DETERMINATION OF SPECIMENS. 57

ttt Pelagic, tadpole-shaped
animals, with long, flat-
tened tail; body with in-
current and excurrent
orifices.

Ascidiacea, sub Preverte-
brata.
titi Minute, transparent pe-
lagic organisms; possess
ing bands of cilia. [Here
belong the larval forms of
Lichinoderms, Nemerteans,
Linteropneusta, some An-
nelids and other marine

Invertebrates. |
NoTE.—Nearly every important group possesses members which live as para-
sites either upon or within the bodies of other animals, and these, especially when
in the latter position, often become so much modified that the usual characteristics
of the groups to which they belong no longer apply to them. In some cases these
modifications are so great that the real affinities may be learned only by a careful
study of the embryological development, in some stage of which the animals are apt
to resemble their free-living allies. Of these modifications the most usual are a
reduction or entire loss of the locomotive organs and those of special sense, and the
acquirement of suckers, hooks, and other adhesive organs; aside from this the gen-
eral shape becomes vermiform or sac-like. It is thus impracticable to attempt to
include the more reduced parasitic forms in the above key, and although many of
them may be found and their position determined by its aid, it will be necessary in
other cases to consult some more special authority. As this key is intended, how-
ever, for the beginning student only, and as the study of these parasitic forms be-

longs to those more advanced in the science, it will doubtless prove a sufficient aid
to those for which it is designed.

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